The invention relates to a pulling device, preferably to pull inwardly and outwardly a blind of a window blind assembly, and including at least one pulling cable that is wound on and off rollers, that engages with ends of the blind to be moved and that exerts a constant pulling force on the cloth by means of a spring element engaging a movable roller. The invention also relates to a window blind assembly incorporating such device.
This general type of pulling device is suitable especially for window blind assemblies, where a blind that protects against the sun is pulled out at least partially horizontally or at a slightly inclined angle. Such known pulling device includes a steel strip which can be wound or unwound over deflecting rollers onto a roller attached coaxially on the side of a shaft onto which the blind is wound. Such strips are positioned at opposite sides of the end of the blind to be moved. To generate the tensioning of the steel strips and thus also the blind, this conventional pulling device includes a deflecting roller which turns each steel strip by 180.degree. and is connected to a gas pressure spring. Such a pulling device is integrated into the guide rails disposed on each side of the blind. However, this device has the drawbacks that with such an arrangement of the pulling device the cross section of the guide rails must be relatively solid and even the shaft for winding the blind must be rather solid on the side thereof with the takeup rollers attached to the shaft for the steel strip. In the case of a window blind assembly, for example that is mounted outside a window in a garden, this can lead to space difficulties. In addition, from an aesthetic point of view it is not ideal if such sturdy guide rails and shafts are required.